1. Field of the Invention
This invention relates to method and apparatus for delivering finished envelopes conveyed horizontally in spaced relationship and transferred to a table where the envelopes are stacked in a compact arrangement on edge and more particularly to a delivery table that maintains the envelopes stacked on edge as the envelopes are delivered to the table and selected quantities of envelopes are periodically removed from the table while the envelopes continue to be transferred on edge to the table.
2. Description of the Prior Art
In the manufacture of envelopes, it is the conventional practice to convey the finished envelopes sequentially either horizontally in spaced apart relation on a conveyor or sequentially in a feed path by rotating cylinders in which the finished envelopes are transferred in the feed path from the surface of one cylinder to the next. The spaced apart finished envelopes are directed individually and sequentially into the slots formed in a conventional delivery spiral which include aligned slotted stacker wheels.
Each slotted wheel includes a plurality of spirally extending fingers which form slots in the periphery of the wheels. The slotted wheels are mounted on a shaft which is rotated in time relation to the mechanism that feeds the finished envelopes sequentially in spaced apart relation. As the envelopes are advanced to the delivery spiral, each envelope moves into a parallel set of slots formed by the extending fingers of each of the aligned wheels.
After the envelope enters the slot it is carried around on the wheels until the seal flap edge of the envelope strikes a delivery table which is positioned down stream of the delivery spiral. The envelopes are transferred from the slotted wheels to a vertical position with the seal flap edge of each envelope positioned downwardly on the delivery table. Generally, the delivery table extends in a horizontal position from the slotted wheels. On the delivery table the finished envelopes are stacked in a compact arrangement where periodically a predetermined number of envelopes are removed for packaging. U.S. Pat. No. Re. 26,348 is representative of known delivery and stacking mechanisms for envelope machines.
U.S. Pat. Nos. 3,116,668; 3,593,486; and 3,641,883 are further examples of envelope delivery and stacking mechanisms in which envelopes are conveyed in a circular path by folding and transfer cylinders that complete the folding operations of the envelope before they are transferred into the slots of a delivery spiral. The envelopes are retained on the surface of the seal fold and transfer cylinders by a suction through vacuum ports. As the envelopes on the delivery cylinder approach the delivery spiral the vacuum force on the envelope is interrupted to release the envelopes and to sequentially transfer them into the slots of the delivery spiral.
From the delivery spiral they are positioned in a stack in a selected position. In one arrangement the envelopes may be stacked with their seal flaps folded and into contact with the delivery table. In another arrangement the envelopes may be stacked with the closure flaps in an opened position and extending upwardly from the table.
Once the finished envelopes are transferred to the delivery table and stacked on edge a predetermined number of the envelopes are periodically removed from the direct feed line. Banding mechanisms are known in which the envelopes in the feed line after stacking are shifted laterally to an adjacent banding mechanism. The banding mechanism automatically bands a pack of predetermined number of envelopes. Generally the lateral movement and subsequent banding is not desired.
Preferably the envelopes are fed in a stack on the delivery table in a direct line of the envelope machine and a predetermined number of stacked envelopes are removed from the feed line. During this process of stacking and removing a predetermined number of envelopes from the delivery table envelopes continue to be transferred from the spiral delivery onto the delivery table. Therefore, the envelopes being transferred onto the delivery table must be maintained in a stacked relationship as a predetermined quantity of stacked envelopes are removed from the feed line. This requires that the envelopes arriving onto the delivery table be maintained in a stacked relation and do not become misaligned as a quantity of envelopes are removed.
U.S. Pat. Nos. 1,791,569; 2,140,112; and 2,232,720 disclose delivery mechanisms in sheet feeding operations, such as envelope machines, which utilize helical feeding devices or screw conveyors. The helices or convolutions are supported by a rotating shaft and are spaced apart to receive the bottom edge of a finished envelope. As the helical conveyor is rotated envelopes are sequentially inserted in the spaces between the helices. The helices propel the envelopes individually in stacked relation onto the delivery table.
In U.S. Pat. No. 2,140,112 as the helical conveyor transfers the envelopes on edge to the delivery table pins projecting from the table engage the lower edges of the envelopes to support the envelopes on edge as they are propelled by the helices to the stack. A stop is positioned on the table in opposed relation to the helices. As the envelopes are added to the stack the stop is pushed by the accumulating envelopes away from the helices but resists such movement and serves to hold the envelopes of the stack compactly together.
The delivery table conventionally uses a conveyor to transport the envelopes in stacked relation from the receiving end of the table to the rearward end where the envelopes are compactly stacked and are removed in a predetermined quantity from the table. This requires that the speed of travel of the stacked envelopes on the table is somewhat slower than the travel of the finished envelopes in the feed line as they approach the spiral delivery. As the envelopes are stacked on edge on the delivery table they are advanced by the conveyor at a speed where the newly arriving envelopes onto the table generate a pushing action against the rear of the stack.
U.S. Pat. Nos. 2,232,721 and 2,787,468 disclose feeding and stacking mechanisms for envelope making machines that utilize gripper mechanisms which engage in timed relation with the operation of the feed conveyor the marginal portion of each envelope as it is transferred on edge to the delivery table. As each envelope is transferred on edge to the delivery table it is added to the stack of envelopes and engaged by a gripping mechanism which holds the envelope compactly in the stack. The gripping mechanism is momentarily released to permit the next envelope to be added to the stack and compacted therewith. As the envelopes are stacked on the table they are supported on a marginal edge by an adjustable side guide and supported in a stacked formation by a slidable stop.
The continued stacking of envelopes on the delivery table must be coordinated with the operation of removing a predetermined quantity of envelopes periodically from the stack. This requires that the envelopes being fed to the table be maintained in a stacked relation as a quantity of stacked envelopes are removed from the rearward end of the table.
Gripper devices and the like are positioned on the surface of the table in the feed line of the envelopes. Their operation must be coordinated with the continued feeding of the envelopes to the table. This necessitates a reduction in the working space available for the operator to remove a quantity of stacked envelopes from the table and increases the complexity of the stacking mechanism. The devices that shift stacked envelopes from the feed line laterally on the delivery table also decrease the operator's access to the stacked envelopes.
Therefore, there is need in envelope stacking mechanisms and particularly in an envelope delivery table for a device that maintains a compact arrangement of stacked envelopes on the table as a predetermined quantity envelopes are periodically removed from the rear as additional envelopes are conveyed to the table. As envelopes are removed, the remaining envelopes on the table must maintained in a compact stacked relationship.